[Laser] Re : Re : reply to Tom regarding low paths over the sea

[f1avyopto at aol.com]

I never compare laser wavelength during my NLOS optical experiments and I did them only near 800 nm in cloud bounce ;
At this wavelength clouds give very strong echoes and the out target losses are very low even during a rainy day.  
To experiment over the sea could be a very powerful way to succeed  a long range NLOS link by using optical super-refraction.
The optical wavelength to use should be the one that gives the lowest losses in  wet air condition.
Of course all the H2O air absorbing lines have to be deselect in this choice.
The best choice could be in the 1500 nm optical window that allows the use of  lasers and photodiodes from the standard optical com devices  ? 
73 Yves
http://f1avyopto.wifeo.com/

 



-----E-mail d'origine-----
De : Chuck Hast <wchast at gmail.com>
A : Free Space LASER Communications <laser at mailman.qth.net>
Envoyé le : Mercredi, 11 Mai 2011 20:14
Sujet : Re: [Laser] Re : reply to Tom regarding low paths over the sea


On Wed, May 11, 2011 at 12:25,  <f1avyopto at aol.com> wrote:
>
> Hello all
> This extended path over sea is not very near the water but is is just an air 
refraction curvature effect or a ducting effect if temperature inverting.
> So it seems to me the spectrum properties in the air mass could be very 
similar a point to point LOS one.
> Have a look about this 250 Km NLOS optical path in France in over sea 
conditions.
> http://jfcoliac.free.fr/Astro/Canigou/canigou.htm
> Use the Google translator to convert Franch to English
> The solar picture is very red because the standard blue absorbing air effect 
but the infrared spectrum could be not deeply changed on the path.
> On 850 nm for to escape the water line loss near 900 nm, this NLOS path seems 
very possible.
> 73.
> Yves F1AVY
> http://f1avyopto.wifeo.com/
>
Yves,
Have you folks tried that path yet?? That would be a interesting one to run
various wavelengths over. I just looked at the overwater path, nice wide
one.

-- 

Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."
---
Home web site:
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